The present invention relates to a photomask, a manufacturing method thereof, a patterning method, and a semiconductor device manufacturing method, and particularly a technique effectively applied to the photolithography using ultraviolet radiation, far ultraviolet radiation, vacuum ultraviolet radiation, or the like as a light source.
To manufacture a semiconductor integrated circuit device (LSI: Large Scale Integrated circuit), a lithography technique is used as a method for forming a micropattern on a semiconductor wafer. In the case of the lithography technique, the so-called optical projective exposure method is mainly used which repeatedly transfers a pattern formed on a photomask onto, a semiconductor wafer through a reduction projection optics. A basic configuration of an exposure system is disclosed in Japanese Patent Laid-Open No. 2000-91192.
A resolution R on a semiconductor wafer in the projective exposure method is generally shown by R=kxc3x97xcex/NA, where k denotes a constant depending on a resist material or a process, xcex denotes a wavelength of illumination light, NA denotes a numerical aperture of a projective exposure lens. As seen by the above relational equation, a projective exposure technique using a light source with a shorter wavelength is required as patterns are made more fine. At present, an LSI is manufactured by a projective exposure system using g-line (xcex=438 nm) or i-line (xcex=365 nm) of a mercury lamp, or a KrF excimer laser beam (xcex=248 nm) as a light source. For the purpose of achieving a finer pattern, it is studied to use an ArF excimer laser beam (xcex=193 nm) or F2 excimer laser beam (xcex=157 nm) having a shorter wavelength.
A normal photomask has a structure in which a thin film made of chromium or the like is formed as a shading film on a quartz glass transparent for exposure light. This photomask is manufactured by applying a resist onto a substrate in which a chromium film is attached to a quartz plate, exposing it in the form of a desired pattern prepared in advance, further developing it to form a resist pattern, and etching the chromium by using the resist pattern. In the case of this normal photomask, because steps of etching a chromium film and of peeling off the resist are required, it takes a lot of time to manufacture the photomask and the cost thereof increases.
Meanwhile, for example, Japanese Patent Laid-Open No. 5-289307 discloses a photomask using not chromium but a photoresist as a shading film. This is a mask using the fact that a photoresist has a shading characteristic relative to short wavelength rays such as ArF rays or the like. Because this technique makes it possible to fabricate a photomask without including a step of etching chromium, an effect of reducing the mask cost can be expected. Moreover, because there is no step of etching chromium, this technique has an advantage in that a pattern dimension accuracy can be ensured.
However, the present inventors have found the following problems in a photomask technique (hereafter referred to as a resist shade mask technique) using a photoresist as the above shading film.
That is, as shown in FIG. 9, a normal resist material has such a problem that it is impossible to obtain a sufficient shading characteristic against rays having a wavelength larger than 230 nm and therefore to completely function as a shading material. That is, the above resist shade mask technique has such a problem that it is impossible to be applied to KrF excimer laser exposure having a wavelength of 248 nm or i-line exposure having a wavelength of 365 nm. FIG. 9 shows OD values in the case of a resist using phenolic resin as a base resin, where the OD values mean values represented by xe2x88x92log10(Iout/Iin) when it is assumed that incident light is Iin and transmitted light is Iout. Moreover, a transmittance T% is represented by 100xc3x97Iout/Iin, OD=xe2x88x92log(T/100). As an OD value increases, the transmittance of light decreases. A resist containing a normal benzene ring has a small OD value in the case of the light having a wavelength larger than 230 nm, similarly to FIG. 9. That is, a sufficient shading characteristic cannot be obtained from the resist because the resist has a high transmittance.
As a finer pattern is achieved, such problems have become more important because the working accuracy of a mask pattern becomes more stringent and the photomask manufacturing cost is increased due to increase of amounts of pattern data. In general, to manufacture one kind of semiconductor integrated circuit device, increase in the photomask manufacturing cost becomes a very large problem because about 20 to 40 photomasks are used, for example.
Under the above situation, however, it is necessary to make a circuit pattern more fine at present in order to improve a semiconductor device in integration degree and in operation speed, and thereby technical development is progressed so as to shorten the wavelength of exposure light. However, if the wavelength of exposure light is shortened, then a material of the lens is a rare and expensive material such as CaF2 and illumination damage of an optical member increases, and thereby component life is shortened. Therefore, short-wavelength exposure light becomes expensive.
Moreover, because a KrF excimer laser beam or an i-line is normally used to manufacture a volume zone for a semiconductor device and the like, an adaptive wavelength in the above resist shade mask technique comes to an important problem. According to a study made by the present inventors, it has been found that when the above resist shade mask technique is used without a sufficient consideration, use of the ArF excimer laser exposure is required everywhere, and even if a photomask becomes inexpensive, the total manufacturing cost rather increases. Therefore, to reduce the cost, it is preferable to apply short wavelength exposure only to steps having such merits that performing fineness exceeds rise in cost and to apply the exposure at a comparatively low cost, to other steps.
Moreover, in the period of system LSIs, the requirement for developing and manufacturing small quantity of various types of LSIs in a short period has been raised. To manufacture LSIs as described above, 20 to 40 photomasks are used. Therefore, a photomask-manufacturing TAT (Turn Around Time) is the motive power of the competition power for developing LSIs, Particularly in the case of a system LSI, because the debugging rate of a wiring layer is high, supplying the photomask of this layer in a short time at a low cost is useful for short-term development of and cost reduction in LSIs.
Moreover, in the case of using a resist as a shade band similarly to the above resist shade mask technique, an ArF excimer laser beam having a comparatively high energy is absorbed by an organic resist material. The absorbed light energy excites organic molecules. Some of the light energy is emitted to the outside as fluorescence and phosphorescence and most of the light energy is emitted to the outside as heat energy. At this time, however, some of the energy may cut a chemical bond between organic molecules or cause reactions with other molecules. As a result, there arise such problems that a resist material serving as a shade band deteriorates in accordance with illumination of an ArF excimer laser beam, and finally loses the function of a shade band.
An object of the present invention is to solve the above problems and to provide a technique capable of developing a small quantity of and various kinds of semiconductor devices in a short time and realizing a photomask most suitable to manufacture the devices at a low cost.
An object of the present invention is to provide a technique capable of realizing a photomask having a sufficient shading characteristic even against exposure light having a long wavelength.
An object of the present invention is to provide a technique capable of shortening time required for manufacturing a photomask.
An object of the present invention is to provide a technique capable of reducing the development period or manufacturing time of a semiconductor device.
An object of the present invention is to provide a technique capable of improving a light-resistant characteristic of a photomask.
An object of the present invention is to provide a technique capable of reducing the manufacturing cost of a photomask.
Further, an object of the present invention is to provide a technique capable of reducing the manufacturing cost of a semiconductor device.
The above and other objects and novel features of the present invention will become more apparent from the description of the present specification and the accompanying drawings.
Of the inventions disclosed in the present application, typical ones will be briefly described as follows.
That is, a photomask according to the present invention has, on a glass plate, a shade pattern containing at least nanoparticles and a binder.
It is proper to use quartz as a glass plate (mask substrate or mask plate) used for a photomask according to the present invention. However, other glass plate or crystal plate may be used if having a higher transmittance than the light used for transferring a pattern through the photomask. Materials of other glass plate or crystal plate include CaF2 and SiO2, for example.
Moreover, the above nanoparticles have each diameter of several xcexcm order or less, and preferably of {fraction (1/10)} the minimum working dimension, and, in this case, of 200 nm or less, and are ones that can scatter light, that is, means ones that can irregularly reflect light. Therefore, a flat metallic sheet made of chromium or the like having a smooth or rough face is not included. Moreover, nanoparticles each have, for example, light refractive index different from a binder. The photomask of the present invention functions as a photomask for preventing transmission of light because nanoparticles contained in the shade pattern scatter light. Fine particles of inorganic matter are used as nanoparticles contained in the shade pattern according to the present invention. Specifically, it is also possible to use fine particles of carbon such as carbon black, graphite or C60, or fine particles of metal oxide such as titanium oxide, aluminum oxide, zinc oxide or the like, or fine particles of a metal such as aluminum, gold, silver, copper or the like. The above particle diameter of 200nm is the maximum value. That is, diameters of nanoparticles contained in a pattern are distributed over the maximum value.
Moreover, the above binder is used to connect the above nanoparticles to each other to form a film, and a polymeric material or organic compound is generally used as the binder. When the photomask according to the present invention is formed, the shade pattern is formed by active radiation. Therefore, the binder utilized in the present invention is one that has any photosensitivity to radiation, namely, that is desirably made of a resist material.
Furthermore, the form of the photomask according to the present invention can be applied to all transmission types of photomasks such as a binary mask, half-tone phase-shift mask, Levenson phase-shift mask and the like which are used a photolithography step. The photomask of the present invention can be used together with such a photomask structure as to use a metallic film such as a chromium film or the like as a shade band in one photomask. That is, it is also possible to use a structure having both a shade pattern formed by a metallic film and the above shade pattern of the present invention in the integrated-circuit-pattern area of one photomask. Thereby, only a predetermined portion on a photomask can be freely changed to a certain extent in a short time. That is, in the case of changing a portion of the photomask, only the portion to be changed can be changed, instead of reforming the entire photomask from the beginning. Therefore, it is possible to easily reproduce or change the photomask in a short time.
In this case where a Levenson phase-shift mask is used, it is preferable that the mask has such a structure as to be called a phase shifter in which a glass plate partially inverts the phase of exposure light (for example, changing the phase by almost 180xc2x0 ). The phase shifter is formed by any one of a denting method of making concavity in a portion of a glass plate that is a photomask plate and thinning film thickness of the portion to invert the phase of exposure light (for example, changing the phase by almost 180xc2x0 ), a method of forming a transparent film having such film thickness as to be capable of inverting a phase (for example, changing the phase by almost 180xc2x0 ) on the glass plate of a photomask, and a method obtained by mixing the above two methods. It is preferable that a shade pattern containing at least nanoparticles and a binder is formed on this phase shifter.
According to a technique studied by the present inventors, the technique is one that an organic material used as a resist material is formed on a glass plate of a photomask as a shade band, and that transmission of the light illuminated on the glass plate is prevented due to absorption of organic molecules at the shade band. This absorption is a specific absorption depending on the chemical structure of a material, and the wavelength of the absorption has a distribution to a certain extent, but is a specific wavelength. In this case, the light energy absorbed by the organic molecules excites the organic molecules. Then, some of the energy changes to heat or fluorescence or phosphorescence from an excited state and is discharged to the outside. However, remaining energy excites the organic molecules and cuts chemical bonds between the organic molecules or reacts with other chemical bonds. Therefore, as light is illuminated, the resist material serving as a shade band deteriorates, and finally loses the function as a shade.
In contrast, in the case of a photomask according to the present invention, nanoparticles contained in a shade pattern scatter the light energy illuminated on the photomask. Some of the light energy is absorbed. However, since scattering is a main function, a small amount of the energy is stored in a pattern portion and thereby deterioration is difficult to cause. Therefore, the life time of the photomask lengthens. Moreover, because the main function of nanoparticles is not absorption, the wavelength to be shaded is not restricted to a specific wavelength. That is, it is possible to obtain such a superior feature that a sufficient shading characteristic which cannot be obtained from the above resist shade mask can be obtained even when not only an ArF excimer layer beam (with wavelength of 193 nm) and an F2 excimer laser beam (with wavelength of 157 nm) but also large-wavelength beams such as a g-line (with wavelength of 436 nm), an i-line (with wavelength of 365 nm), and a KrF excimer laser beam (with wavelength of 248 nm) are used as exposure light. That is, as seen from different operation described above, the present invention is a technique completely different from a photomask using a resist film as a shade band, in operation, configuration, and effects.
Moreover, by using, as the above nanoparticles, any one of inorganic matter, metal, and metal oxide that are more stable than organic matter in light energy and heat energy, there are such superior advantages that a chemical change is difficult to make relative to exposure light or the like, and that deterioration is difficult to make in the case of being used as the photomask. As the above inorganic matter, there is, for example, carbon, graphite, C60 or the like. Moreover, as the above metal, there are, for example, gold (Au), silver (Ag), copper (Cu), aluminum (Al) or the like. Furthermore, as the above metal oxide, there are, for example, titanium oxide, aluminum oxide, zinc oxide or the like. Besides, pigment or dye may be used as the nanoparticles.
It is preferable to use fine particles of carbon such as graphite or C60 as the above nanoparticles. A shade pattern containing fine particles of carbon such as graphite or C60 can be removed through ashing. Therefore, there is such a superior advantage that a quartz or glass plate can be reproduced from a photomask having been once formed, by ashing.
Moreover, in the case of selecting the above metal or metal oxide as nanoparticles, simplicity of a process can be achieved. Moreover, there is such a superior advantage that it is possible to improve the dimension accuracy of the shade pattern.
Furthermore, in the case of using conductive inorganic matter, metal, or metal oxide as nanoparticles, it is possible to provide conductivity for a shade pattern. In this case, because the charge-up thereof can be reduced or prevented at the time of performing the electron-beam writing for patterning the shade pattern, it is possible to improve the pattern writing accuracy. Therefore, because the pattern dimension accuracy of a semiconductor device can be improved, it is possible to further improve the performance of the semiconductor device, and achieve development of the fineness and the integration degree of the device.
The shade pattern of the photomask according to the present invention may include dye molecules which absorb the light in addition to nanoparticles as components for transmitting no light. In this case, it is possible to reduce the quantity of nanoparticles to be contained, and thereby to obtain a high resolution. However, in the case where contribution of dye is large or only dye is simply contained as a material for shading light, light energy is absorbed by dye molecules and may cause both excitation of the molecules and any chemical reaction, and thereby absorbance may change. However, in the present invention, because the above nanoparticles are used together with others, such drawbacks can be difficult to cause or are not caused. That is, the present invention is greatly different, in configuration, from a photomask having a pattern with a shading characteristic obtained by merely making a resist film which contains light dye, and can improve the light-resistant characteristic better than the case of adding only the dye. Therefore, it is possible to improve the service life of the photomask.
It is preferable that the transmittance of the shade pattern portion of the present invention is 16% or less when a wavelength is 100 nm or more and 500 nm or less. In the case where a half-tone phase-shift mask is used as a photomask, it is preferable that the transmittance of the above shade pattern has a range of 2% to 16%, particularly preferable that the transmittance has a range from 4% to 9%. Moreover, in the case where a binary mask is used as a photomask, it is preferable that the transmittance of the above shade pattern portion is 1% or less, and more preferable that the transmittance is 0.5% or less, and particularly the most preferable that the transmittance is 0.1% or less. Furthermore, even in the case of a Levenson phase shift mask, it is preferable that the transmittance of the above shade pattern is 1% or less when a wavelength is 100 nm or more and 500 nm or less, and more preferable that the transmittance is 0.5% or less, and particularly the most preferable that the transmittance is 0.1% or less.
As previously described, to realize a low cost, it is preferable that a light source used for lithography has a longer wavelength. Therefore, it is preferable that the transmittance of the above shade pattern is 16% or less when a wavelength is 100 nm or more and 700 nm or less. Also in this case, if a half-tone phase shift mask is used as a photomask, then it is preferable that the transmittance of the shade pattern has a range from 2% to 16%, and particularly more preferable that the transmittance has a range from 4% to 9%. Moreover, in the case where a binary mask is used as a photomask, it is preferable that the transmittance of the shade pattern is 1% or less, and more preferable that the transmittance is 0.5% or less, and particularly the most preferable that the transmittance is 0.1% or less. Furthermore, even in the case of a Levenson phase-shift mask, it is preferable that the transmittance of the shade pattern is 1% or less when a wavelength is 100 nm or more and 700 nm or less, and more preferable that the transmittance is 0.5% or less, and particularly the most preferable that the transmittance is 0.1% or less. The above transmittances can be freely changed to a certain extent by changing the bending ratio between nanoparticles and a binder to be contained in the shade pattern. Moreover, they can be freely changed to a certain extent by changing the film thickness of the shade pattern. Furthermore, needless to say, they can be freely changed to a certain extent by changing both the blending ratio and the thickness.
In the case of shading light by using nanoparticles as previously described, shading the light is performed not by absorbing the light by a material thereof but mainly by scattering the light, and so the wavelength of the light to be shaded is not restricted to a specific wavelength. Therefore, at the time of forming a pattern through the exposure using a photomask of the present invention, it is possible to select a light source or an exposure system suitable for dimensions of a pattern to be transferred or for a manufacturing process thereof or the like, without restricting a usable light source or exposure system or the like which depends on a photomask. Therefore, it is possible to achieve improvement of both the pattern-dimension accuracy and reliability of a semiconductor device.
Moreover, there is the case of using visible light such as a helium-neon laser beam having a wavelength of 633 nm, for positional detection of a photomask. Even in such case, there is such an advantage that it is possible to easily detect the shade pattern having a transmittance of 16% or less when a wavelength is 100 nm or more and 700 nm or less.
Furthermore, each particle diameter of nanoparticles according to the present invention is made smaller than the minimum working dimension of the shade pattern, and preferably made to be {fraction (1/10)} the minimum working dimension or smaller. Specifically, it is preferable to use a nanoparticle, for example, having a particle diameter of 200 nm or less, and more preferable to use a nanoparticle having a particle diameter of 100 nm or less. It is the most preferable to use a nanoparticle having a particle diameter of 50 nm or less. It is possible to use a nanoparticle having a particle diameter exceeding 200 nm. However, when each particle diameter is too large, a sufficient accuracy of the photomask is difficult to obtain because roughness of the sidewall of a pattern formed as the photomask increases. Moreover, when the particle diameter is too large, the nanoparticles contained in the shade pattern cannot scatter the light properly (uniformly). Each particle diameter of the nanoparticles contained in the shade pattern does not easily uniform, and so the nanoparticles having various particle diameters are contained. The particle diameter of 200 nm shown above is the maximum value and a distribution of particle diameters appears over the maximum value. Respective particle diameters of nanoparticles contained in the shade pattern may be equal or almost equal to each other. However, by containing both nanoparticles having relatively large particle diameters and those having relatively small particle diameters in the shade pattern, it is possible to distribute respective small nanoparticles between large nanoparticles. That is, it is possible to fill gaps between the large nanoparticles, with the small nanoparticles. Thereby, it is possible to change the transmittance of the above exposure light. Moreover, it is possible to reduce the transmittance of the exposure light in comparison with the case of constituting a shade pattern by only large nanoparticles. A particle diameter in this case means one measured as a nanoparticle or a group of nanoparticles at the time of measuring nanoparticles. Therefore, there are a case of the particle diameter of one nanoparticle and also a case of the diameter of an aggregate constituting a plurality of nanoparticles.
Furthermore, according to the present invention, it is preferable that the content of nanoparticles in a shade pattern containing at least nanoparticles and a binder is, for example, 10% or more and 99% or less out of the solid content of the shade pattern. To form the shade pattern, a binder occupies a certain amount because nanoparticles and a binder are normally combined with each other. However, by providing heat energy similarly to a sintering treatment after formation of a pattern, it is possible to reduce the binder part therein and increase the content of nanoparticles therein. Moreover, a shade pattern may be formed only by nanoparticles, with the binder part being almost zero or nothing.
Furthermore, it is possible to provide a protective film (a protective means) generally referred to as a pellicle, to the photomask of the present invention after formation of the photomask.
Furthermore, in the case where the photomask of the present invention is a Levenson phase-shift mask having a phase shifter, the phase shifter can be obtained by forming a coated-glass SOG (Spin On Glass) film at a predetermined position located on a glass plate so as to have a predetermined film thickness. Moreover, the phase shifter may be obtained by making concavity in a glass plate at a predetermined position up to a predetermined depth.
Furthermore, in both a photomask and a manufacturing method of the photomask according to the present invention, by simple steps of forming, exposing and developing a film containing at least nanoparticles and a binder, the photomask can be manufactured at a low cost in a short time. Moreover, because a sputtering step of using a vacuum system at the time of widely attaching a metallic film such as a chromium film or a step of etching the metallic film is not used, a yield for manufacturing the photomask is improved. Furthermore, by using nanoparticles made of the above carbon, carbon black, C60 or the like, even after use of the photomask, the used photomask can be completely reproduced into a state of blanks through ashing or solvent treatment, and therefore this is effective in recycling of resources and reduction in the photomask cost.
Furthermore, a photomask manufacturing method of the present invention comprises the steps of: forming, on a glass plate, a film containing at least nanoparticles and a binder; exposing the film; and developing the film to form a shade pattern.
Furthermore, it is preferable to use quartz for a glass plate used in a photomask manufacturing method of the present invention. However, the glass plate is not restricted to quartz, and can make various modifications, and may be other glass pate or crystal plate as long as transmittance is very high relative to the light used to transfer a pattern through the above photomask. Furthermore, to enhance the adhesiveness between a glass plate and a resist material, a treatment step of accelerating the bonding between them such as a step of applying a hexa-methyl-disilazane (HMDS) treatment to them may be added.
Furthermore, a photomask manufacturing process of the present invention can be applied to all the transmission types of photomasks including a binary mask, a half-tone phase-shift mask, a Levenson phase-shift mask and the like which are used in a photolithography step. Among phase-shift masks, a Levenson phase-shift mask in which both a structure for partially inverting the phase of exposure light (e.g. inverting the phase by about 180xc2x0 ) and a shade band for preventing the exposure light from making transmission are formed on a transparent plate, can be formed by the following three kinds of methods.
First, in the case of forming a phase shifter by photo-reactive glass, the phase shifter is formed by the steps of: forming photo-reactive glass on a mask basic substance; exposing and developing the photo-reactive glass to form a phase shifter with a predetermined film thickness at a predetermined position thereof; forming, on the phase shifter, a film containing at least nanoparticles and a binder; and exposing and developing the film to form a shade pattern.
Moreover, in the case of forming a phase shifter by coated glass having no photosensitivity, the phase shifter is formed by the steps of: forming a coated-glass film on a mask basic substance; coating a resist onto the coated-glass film; exposing and developing the resist to form a resist pattern; etching the coated-glass film by using the resist pattern as a mask; removing the resist pattern to form a phase-shifter pattern, forming, on the phase-shifter pattern, a film containing at least nanoparticles and a binder; and exposing and developing the film to form a shade pattern.
Furthermore, in the case of making concavity in a transparent glass plate itself to form a phase shifter, the phase shifter is formed by the steps of: coating a resist onto a mask basic substance; exposing and developing a desired shifter pattern on the resist to form a resist pattern; treating the mask basic substance by using the resist pattern as a mask; removing the resist pattern to form a phase-shifter pattern; forming, on the phase-shifter pattern, a film containing at least nanoparticles and a binder; and exposing and developing the film to form a shade pattern.
In the case where a photomask to be formed is a normal binary mask or a half-tone phase-shift mask, the step of treating the above phase shifter is not required.
Moreover, in a photomask of the present invention, it is possible to use a chromium film or the like as a shade band, with a shade pattern containing at least nanoparticles and a binder. In this case, after a shade band made of chromium or the like, except for a predetermined portion of a photomask by a generally known method. A shade pattern containing at least nanoparticles and a binder may be formed only on the predetermined portion by the above method. In the case of the above photomask structure, a shade pattern formed by a metallic film and the above shade pattern containing nanoparticles are arranged on one photomask.
Furthermore, a material for forming a shade pattern used for a photomask manufacturing method of the present invention is characterized by containing at least nanoparticles and a binder. In this case, the binder is used to form a film by connecting the nanoparticles to each other, and polymer or organic compounds are generally used as the binder. In the case of manufacturing of the photomask of the present invention, a shade pattern is formed by actinic irradiation. Therefore, it is preferable that the binder used for the present invention is made of a material having photo-sensitivity to the radiation, which is a resist material. Therefore, a material, in which nanoparticles are dispersed in a resist material using polymer or organic materials, may be used. In this case, the term xe2x80x9cdispersedxe2x80x9d means such a state that fine particles float in a resist solution. To prevent fine particles from settling, floating or becoming un-uniform in a dispersed state, it is preferable to add a dispersant for helping dispersion as occasion demands. The resist material has a positive type one in which an exposed portion is removed through development, and a negative type one in which an unexposed portion is removed through development. Either of them may be used as occasion demands. Because the nanoparticles used in this case are also the same as those above described, the description thereof will be omitted.
Also in the case of a photomask manufacturing method of the present invention, the transmittance of the above exposure light is the same as one previously described. Therefore, the description thereof will be omitted. Moreover, because particle diameters of the nanoparticles are the same as those previously described, the description thereof will be omitted.
Furthermore, any light source or beam source, which is used for a step of exposing a film containing at least nanoparticles and a binder used for a manufacturing method of the photomask according to the present invention, may be used as long as it emits active radiation. However, in the present invention, a resist film contains at least nanoparticles, and thereby there are some cases where the exposed light may not reach the bottom of the film. Therefore, in the case of using the light for manufacturing the photomask, it is necessary to select a proper wavelength.
From the above reasons, it is preferable to use one of an electron-beam writing system and an ion-beam exposure system and the like, as a system for emitting active radiation used for exposure. In the case of the exposure by the electron-beam writing system or ion-beam exposure system, the exposure is different from exposure by light and an exposure beam reaches the lower portion of a film. Therefore, a pattern can be easily formed. Moreover, these systems each have such an advantage that it is possible to generate an active radiation having a desired shape without passing through a photomask and to selectively apply the active radiation to a predetermined portion.
In the case of writing a pattern by an electron beam of the above electron-beam writing system, it is preferable to form a discharge layer for preventing charge-up thereof on a film containing at least nanoparticles and a binder. Moreover, in the case where a step of forming a phase shifter is included in a photomask manufacturing method, it is preferable to form a discharge layer on a resist for treating the phase shifter.
Moreover, in a photomask manufacturing method of the present invention, a plate provided with a film containing at least nanoparticles and a binder may be heat-treated before development and after exposure. In the case of using a chemical amplified resist film as a binder, it is possible to accelerate a reaction by performing the above heat treatment. Therefore, it is possible to easily form a pattern and to sufficiently exhibit a function as a resist.
Furthermore, in a photomask manufacturing method according to the present invention, any developer may be used as long as the developer can develop a film containing at least nanoparticles and a binder. It is better to use an aqueous alkali solution than an organic solvent as a developer. As the aqueous alkali solution, it is possible to use an aqueous nonmetallic-alkali solution such as tetramethylammonium hydroxide or an aqueous alkali-metal-containing alkali solution such as sodium hydroxide, or potassium hydroxide. Moreover, water may be used as a developer if the water can have a development function.
Furthermore, it is preferable that the above aqueous alkali solution contains a surface active agent in order to improve the development characteristic. As the surface-active agent, there is alkylsulfate sodium salt, polyoxyalkylene, tetraalkylammonium halide or the like. By adding these surface-active agents to an alkaline developer, it is possible to prevent a residue remaining at the time of development. When development is performed by the above developer, a spray development may be used, or an immersion-type development may be performed. Moreover, ultrasonic waves may be utilized during development in order to prevent a residue remaining at the time of development. It is possible to improve a cleaning effect by the above ultrasonic-wave treatment. Particularly, in the case of the present invention, because the present invention contains the above nanoparticles, the ultrasonic-wave treatment is effective in removal of the nanoparticles.
Furthermore, in a photomask manufacturing method of the present invention, it is possible to improve the light-resistant characteristic of a photomask by giving energy to a shade pattern formed after a step of developing a film containing at least nanoparticles and a binder. Though the above shade pattern contains at least nanoparticles and a binder, it is also possible to reduce the content of a binder portion by giving heat energy like a sintering treatment after formation of a shade pattern. Moreover, it is possible to make the content of the binder portion almost zero (such a state that the nanoparticles contained in the pattern is relatively more than the binder in content.) or nothing. It is also effective to heat-treating a shade pattern while the pattern is illuminated with ultraviolet radiation (DUV rays), in order to prevent the pattern from being deformed. At this time, preferably, it is possible to raise the heat-treatment temperature, for example, up to about 250xc2x0 C., and it is possible to further improve the light-resistant characteristic.
Furthermore, in the case of a photomask manufacturing method of the present invention, it is possible to provide a protective film generally called a pellicle after formation of the mask.
Furthermore, a pattern forming method of the present invention comprises the steps of: forming, on a substrate to be treated, a film formed of a photo-reactive composition; exposing a photo-reactive composition film through a photomask on which a predetermined pattern is formed; and developing the photo-reactive composition film to form a pattern of the photo-reactive composition on the substrate to be treated, wherein the photomask is constituted so as to have, on a glass plate, a shade pattern containing at least nanoparticles and a binder.
Because a glass plate of a photomask used in a pattern forming method of the present invention is the same as one mentioned above, the description thereof will be omitted.
A photomask used in a pattern forming method of the present invention functions as a photomask similarly to one described above because nanoparticles contained in a shade pattern disperse light. A pattern forming method of the present invention can be applied to all the transmission types of photomasks including the above binary mask, half-tone phase-shift mask, Levenson phase-shift mask and the like. Moreover, as described above, the method can be applied to such a photomask as to have both a shade pattern formed by a metal and a shade pattern formed by a film containing the above nanoparticles. Because the configuration of the Levenson phase-shift mask is the same as one mentioned above, the description thereof will be omitted.
Because operations and effects of the photomask used in the pattern forming method are also the same as one mentioned above, their description will be omitted. Moreover, because material (including modifications) and particle diameters of the nanoparticles, and transmittance relative to exposure wavelength of the nanoparticles, and detective position of a photomask, and the configuration in which both the content of nanoparticles and the binder are reduced, are also the same as one mentioned above, their description will be omitted.
In the case of a pattern forming method of the present invention, it is preferable that wavelength of the light used to expose a photo-reactive composition film on a wafer is 100 nm or more and 700 nm less. In the case of using a larger exposure-light wavelength, for example, it is possible to use a high-pressure mercury-vapor lamp as a light source, and so realize a low cost because a light source or an exposure system is comparatively inexpensive. However, because a resolution relates to a wavelength, the resolution is not improved if an exposure wavelength is a large wavelength. In contrast, in an exposure system using, as a exposure light, a small wavelength such as an ArF or KrF excimer laser beams or the like, the price thereof is high in the existing circumstances but the resolution is further improved for reduction in the wavelength and a fine pattern can be formed.
Moreover, in the case of a pattern forming method of the present invention, similarly to one mentioned above, a photo-reactive composition film may be heat-treated before development and after exposure. As described above, when the photo-reactive-composition film is made of a resist using an acid catalyst called a chemical amplified resist, the above heat treatment is required to progress a chemical reaction.
Furthermore, in the case of a pattern forming method of the present invention, it is preferable that a developer is a water alkaline developer because the developer does not greatly influence the natural environment.
Furthermore, a semiconductor device manufacturing method of the present invention includes the steps of: forming a resist pattern on a semiconductor substrate by any one of the above pattern forming methods; and etching the semiconductor substrate in accordance with the resist pattern or implanting ions into the semiconductor substrate.
As an etching method used in a semiconductor device manufacturing method of the present invention, any one of dry etching methods such as a plasma etching, a reactive-ion etching, a reactive-ion-beam etching methods or the like, and a wet etching may be used.
Moreover, as a substrate to be treated by a semiconductor device manufacturing method according to the present invention, any one of a silicon-dioxide film formed by a CVD (Chemical Vapor Deposition) method or a hot oxidation method, and an oxide film such as an applied glass film, and a nitride film such as a silicon nitride film may be used. Moreover, any one of various types of metallic films made of aluminum, an aluminum alloy, and tungsten or the like, and a film made of polysilicon, and the like may be used.
Furthermore, in the case of a semiconductor-device manufacturing method of the present invention, it is possible to form a photomask used in the method, at a low cost in a short time. As a result, it is possible to manufacture a semiconductor device at a lower cost in a quick TAT (Turn-Around-Time).